Without Phil Vickery because of back trouble, the inclusion of Powell is vital against Bath's excellent pack of forwards.
"Gary has been a concern to us but it is significant he has come through okay," Ryan told www.gloucesterrugby.co.uk. "He is a specialist tight-head and without Phil Vickery, he is someone we need available to us at this stage of the season.
"I am sure Bath will test us significantly up front - they have a very powerful front eight - and we know it will be a very big challenge in the forwards.
"But these occasions are something we should relish. They are intense encounters but great games all the same. We have already lost to Bath twice this season, once to a last minute penalty in the Premiership and again in the Powergen Cup when they produced a more complete performance, so we don't want to for a third time.
"They have developed a more all-round game since Brian Ashton has been involved and are a threat all over the field. They now play a more rounded game and in my opinion that presents us with more of a threat."
Ryan has also made a change in the second row with Adam Eustace returning to the number four shirt in place of Jonathan Pendlebury, who moves to the bench.
In the back row, a hamstring injury sidelines Peter Buxton which means Jake Boer - closing in on 150 Premiership appearances - will switch from number eight to the blindside flank to accommodate Adam Balding.
Andy Hazell, who was excellent against Newcastle, starts at openside.
The backs show only one change from the victory over the Falcons. Mark Foster, who missed the trip because of a painful wisdom tooth, returns to the wing which means James Simpson-Daniel shifts to the centre alongside Rudi Keil.
Terry Fanolua is named in the bench while both Mike Tindall and Mefin Davies are on international duty with England and Wales respectively.
"Every year when you come to Gloucester-Bath games, people expect something to happen and this season is no different," Ryan added. "I am thoroughly looking forward to it - these games are the reason we are involved in the sport and want to do well."
The one addition to the bench is Luke Narraway, who will provide Gloucester with plenty of options in the back row.
GLOUCESTER (v Bath, tomorrow, 12pm): Jon Goodridge; James Bailey, James Simpson-Daniel, Rudi Keil, Mark Foster; Ludovic Mercier, Peter Richards; Patrice Collazo, Rob Elloway, Gary Powell, Adam Eustace, Alex Brown, Jake Boer (capt), Andy Hazell, Adam Balding. Reps: James Parkes, Nick Wood, Jonathan Pendlebury, Luke Narraway, Simon Amor, Terry Fanolua, Brad Davies.